Field of the Invention
The present invention relates to a magnetic head for use of a floppy disc drive(FDD) and a hard disc drive(HDD).
Related Art
One example of a conventional magnetic head for HDD is illustrated in FIGS. 5-7. In FIG. 5, a magnetic head 1 is comprised of in general an approximately rectangular slider 4, on one side of which rail portions 2, 3 (hereinafter referred as "the first rail and the second rail" respectively) are provided to slide on a magnetic medium (not shown), an approximately rectangular hole 5 formed on the first rail 2 of the slider 4, a front core 8 to be inserted in the hole 5, sealed with such as glass and provided with magnetic gaps (a read/write gap 6 and an erasing gap 7), a back yoke 10 made of magnetic material, which contacts to the front core (a head core body) 8 and forms a head core 9, and read/write coil 11 and erasing coil 12 which are mounted on the later-described leg portions of the back yoke 10.
Between the first rail 2 and the second rail 3, a groove 13 which is positioned on a level lower than the level of these first and second rails 2 and 3 is formed.
The front core 8, as shown in FIG. 7, is formed in general with a first core member 14 having a read/write gap 6 on one side of the member 14 and a second core member 15 having a side core 17 connected to the first core member 14, which is approximately figure rectangular in order to be inserted in the rectangular hole 5.
The first core member 14 is formed in general with a first center core 16 being made of magnetic material and elongating to the other side of the front core 8 and the magnetic material-made side core 17 for reading and writing and positioned on the front side.
The second core member 15 is formed in general with a second magnetic material-made center core 18 to be elongated to the other side of the front core 8 and connected to the first center core 16 and the magnetic material-made side core 19 for erasing use, being positioned on the front side and elongating to the other side of the front core 8 connected to the second center core 18 through an erasing gap 7. The second core member 15 is positioned to the same height level as the first core member 14. And, in the figures, 20 is glass which provides magnetic insulating and connection.
The back yoke 10, as shown in FIG. 5, is formed in general with an annular and approximately rectangular closed body 21, a stepped portion 22 which is extended corresponding to the opening side of the closed body 21 and provided on the bottom of the closed body 21, and first, second and third leg portions 23, 24 and 25 which are standing at the edge portion of the stepped portion 22.
The first leg portion 23 is coupled with the read/write coil 11, the third leg portion 25 is coupled with the erasing coil 12.
And, the first and third leg portions 23 and 25 are connected to the read/write side core 17 and the erasing side core 19 (FIG. 7) which are positioned on the front side, and the second leg portion 24 is connected to the first center core 16 and the second center core 18, and as shown in FIG. 6 the front core 8 and the back yoke 10 are unified, thereby the head core 9 is formed with the first, second and third leg portions 23, 24 and 25, the back yoke 10 including the stepped portion 22 and the front core 8.
A first side wall portion 21a and a second side wall portion 21b which are located on the line along which the first, second and third leg portions 23, 24 and 25 are disposed are provided with cut outs 26, 26, and lead wires 11a and 12a for the read/write coil 11 and an erasing coil 12 are adapted to be drawn out.
Further, perpendicular to the first side wall portion 21a, and second side wall portion 21b, a third side wall portion 21c and a fourth side wall portion 21d are formed. On the third side wall portion 21c, first, second and third ribs 27, 28 and 29 are formed in such a manner that these ribs correspond to the first, second and third leg portions 23, 24 and 25 respectively.
In this magnetic head, the front core 8 forming a part of the head core 9 is inserted in the hole 5 to seal the front core 8 to the slider 4, and molten glass is poured between the front core and the slider 4 avoiding any void from being generated. It also prevents matter such as dusts from being entered between such voids, thereby it is prevents the property from being deteriorated.
By the way, in the above mentioned conventional art, prior to the entering of the front core 8 into the slider 4, the slider 4 is adapted to be sintered, but by this sintering, as shown in FIG. 8, there have been generated such deformation in one of the inner walls of the hole 5 which are positioned on the long side of the central portion thereof causes to make the hole 5 larger or, to the contrary to the illustration as shown in FIG. 8, such deformation of the central portion thereof is projected inside of the hole 5 to make the hole 5 smaller.
Thereby, when the front core 8 is inserted in the hole 5 and the hole 5 is filled with glass, the front core 8 moves freely in the hole 5 and it is difficult to fix the front core at a given position.
As another conventional example, there is a magnetic head 1 which comprises, as shown in FIG. 9, four inner walls 30a, 30b, 30c and 30d forming the hole 5 (hereinafter referred as "first, second, third and fourth inner wall respectively), on the center of the first inner wall 30a, a stripe of projection (hereinafter referred as "first projection ") 31a extending in a longitudinal direction of the hole 5 (in the direction perpendicular to the paper of FIG. 9) is formed and on the second inner wall 30b two stripes of projections (hereinafter referred as "the second projection") 31b, are formed the height of which is the same as the first projection. In this case, the sectional view of the first and second projections 31a, 31b show these being round and taller at the center portions thereof.
In the magnetic head 1 of FIG. 9, when glass is poured into the hole 5, between the first inner wall 30a and the second inner wall 30b on which the first projection 31a and the second projection 31b are formed and the front core 8, compared with the plain sides of the third inner wall 30c and the fourth inner wall 30d, excessive amount of glass flows toward the third inner wall 30c and the fourth inner wall 30d, and due to the difference of the surface tension of the blowed glass, the head core 9 tends to be displaced as being attracted toward the third inner wall 30c and the fourth inner wall 30d and thereby the position of the front core 8 is determined.
However, since the difference of the size of a gap G.sub.3 4 between the third and fourth inner walls 30c, 30d and the front core 8, and the size of a G.sub.1 2 between the first and second inner walls 30a, 30b and the front core 8 becomes large, each amount of the glass blowed in the two gaps G.sub.3 4, G.sub.1 2 does not become even with each other.
That is, if the viscosity of the glass is smaller than the most preferable one, the molten glass is apt to flow excessively in the gap G.sub.1 2 which is formed between the first and second inner walls 30a, 30b and the front case 8 and larger than G.sub.3 4, and it is threatened to be blowed away.
To the contrary, if it is larger, the molten glass does not flow suitably in the gap G.sub.3 4, which is formed between the third and fourth inner walls 30c, 30d and the front core 8, and smaller than G.sub.1 2.
And, in order to solve the above problem which the magnetic head 1 of FIG. 9 has, it can be conceived that, as shown in FIG. 10, corresponding to one projection (the first projection 31a) of the first inner wall 30a and two projections (the second projection 31b) of the second inner wall 30b, on the third and the fourth inner walls 30c, 30d respectively also, one projection (the third projection 31c) and two projections (the fourth projection 31d) are provided to form the magnetic head 1. And, according to the magnetic head 1 shown in FIG. 10, since all of the inner walls (the first, second, third and fourth inner walls 30a, 30b, 30c and 30d) are provided with projections, the flow of the molten glass becomes easy to be controlled.
However, when all of the inner walls (the first, second, third and fourth inner walls 30a, 30b, 30c and 30d) are provided with projections, as to the positioning of the front core 8 within the hole 5, the circumstance becomes the same as the one in the case of the magnetic head 1 shown in FIGS. 5-8, and thereby, it is not determined to solve the problem appropriately.